Transition Metal Complexes of 3-Cyano- and 3-Nitroformazans

Abstract

The synthesis and characterization of six transition metal complexes of 3-cyano- and 3-nitroformazans are described. Three different formazans were reacted with nickel(II) to produce complexes with bidentate formazan ligands. Mononuclear NiL2 (L = deprotonated formazan) or binuclear hydroxo-bridged (LNi)2(mu-OH) 2 species were produced depending on the steric bulk on the formazan N-aromatic substituents. 1,5-Bis(2-methoxyphenyl)-3-cyanoformazan acts as a tetradentate monoanionic ligand in a copper(II) complex, whereas the analogous 1,5-bis(2-hydroxyphenyl)-3-cyanoformazan binds as a trianion in a tetradentate manner to Fe(III) and Co(III). Crystal structures-the first examples of metal complexes of cyano- or nitroformazans-as well as the electronic spectra of the complexes are discussed in relation to each other as well as that of the uncoordinated formazans.

Formazanido complexes of heavier group 13 elements aluminium, gallium, and indium

“…The determined absorption maxima and extinction coefficients are in agreement with reports of Berry et al 6 and Gilroy et al 12,25 They attribute the red shift of the complexes compared to the protonated neutral formazans to the fixed conformation and the anionic character of the ligand moiety. The comparison of our studies with a literature known boron complex shows that the higher aluminium, gallium, and indium analogues (2, 3, and 4, respectively) absorb increasingly more red-shifted (Scheme 7).…”

Effects of Electron-Deficient β-Diketiminate and Formazan Supporting Ligands on Copper(I)-Mediated Dioxygen Activation

“…The formazan-Cu metallocycle appears as a boat-like conformation due to displacement of the central carbon and the Cu atom away from the plane defined by the formazan N atoms. Similar conformational properties have been seen for related formazan complexes 11,13,35…”

Solvatochromic Behaviour of Formazans and Contribution of

“…The hydrazone-type intermediates are then deprotonated (by hydroxide or initial carbanion) and the resulting carbanion attacks a second equivalent of aryl-diazoniumcation, yielding a variety of highly coloured compounds 23 .…”